With respect to authentication for access to a specified server on the internet, the Patent Document 1 discloses a callback authentication system which uses a telephone number instead of a user ID. In such the callback authentication system, an authentication device recognizes that a telephone number received from a user's terminal device together with an authentication request is previously registered and has access authority. Without any problem, the authentication device calls back to the telephone number and authenticates an identical person.    [Patent Document 1] Japanese Published Unexamined Patent Application No. 2006-33780